Arc-trapping improvement for electric switch cases

ABSTRACT

An electric switch case with an actuator extending through the cover thereof and an insulating shield surrounding that portion of the toggle element in the interior of the case for taping arc discharges formed by the opening of electrical circuits therein.



1. An electric switch comprising a boxlike case, at least one electrical circuit element in said case, a contact element within said case movable between alternative positions into contact with and apart from said circuit element for closing and opening its electrical circuit, the opening of said electrical circuit normally producing an arc discharge between said circuit element and said contact element, a roof portion made of insulating material enclosing the top of said case, an actuator element extending from the exterior of said case through said roof portion into the interior of said case for producing the switching motion of said contact element, and a shield of insulating material on said roof portion surrounding the area where said actuator element extends through said roof portion and extending partially into the interior of said case, said shield being located in a position near the end region of the case to form an arc-trapping compartment located substantially directly above said circuit element and causing an arc spark to be deflected and to be quenched upon the outer end portion of said contact element, said shield forming a barrier between said arc discharge within said case and said element.
 2. A switch according to claim 1 and furtheR comprising a slot in said roof portion within which said actuator element is movable from one switch position to another and wherein said shield comprises a boss integrally formed on said roof portion around said slot and extending into the interior of said case a sufficient distance to prevent an arc discharge formed by the opening of said electrical circuit to impinge upon said actuator element.
 3. A switch according to claim 1 and further comprising a slot in said roof portion through which said actuator element extends and wherein said actuator element is made of metal and said shield extends into the interior of said case and forms a skirt around that portion of the actuator element that extends into the interior of said case a sufficient distance to prevent an arc discharge formed by the opening of said electrical circuit to impinge upon said actuator element.
 4. A switch according to claim 1 and further comprising a slot in said roof portion through which said actuator element extends and wherein said actuator element is made of metal, and said shield comprises a pair of spaced-apart laterally extending bosses formed on said roof portion at opposite ends of said slot, said bosses extending downwardly into the interior of said case a sufficient distance to prevent an arc discharge formed by the opening of said electrical circuit within the interior of said case impinging upon said actuator element.
 5. A switch according to claim 1 wherein there are two spaced-apart electrical circuit elements mounted in the interior of said case and wherein said contact element comprises a lever pivotally mounted between said two circuit elements, said lever being movable into alternative positions for closing the electrical circuit of one of said circuit elements, and opening the electrical circuit of the other of said circuit elements.
 6. An electric switch according to claim 1 wherein said circuit element is located at the bottom end region of said case and said shield is located in a position spaced apart from the top end region of said case to form an arc-trapping compartment substantially directly above said circuit element.
 7. An electric switch according to claim 1 wherein said case comprises a pair of identically formed sections juxtaposed against each other to form said case, an opening in the top of said case through which said actuator element extends, a recess in one end portion of the roof portion of each of said sections, an integrally formed projection in the other end portion of said roof portion, the roof portion projection of each of said sections nesting within the roof portion recess of the adjacent case section whereby a barrier is formed across the central seam line between said juxtaposed case sections to prevent arc discharge from penetrating into and through said seam line, and integrally formed laterally extending bosses formed at the opposite ends of said opening, said bosses extending downwardly into the interior of said case a sufficient distance to prevent an arc discharge formed by the opening of an electrical circuit within the interior of said case from impinging upon said actuator element.
 8. An electric switch in the form of a boxlike case enclosing electrical switching elements, said case comprising a pair of juxtaposed identically formed case sections formed of insulating material and forming a seam line therebetween, at least one electrical circuit element in said case, a contact element within said case movable between alternative positions into contact with and apart from said circuit element for closing and opening its electrical circuit, the opening of said electrical circuit normally producing an arc discharge from between said circuit element and said contact element, the top portions of each case element together forming a roof enclosing the top of said case, an actuator element extending through said roof into the interior of said case for producing the switching motion of said contact element, a barrier integrally formEd on the interior surface of said roof and extending inwardly into the interior of said case surrounding the area where said actuator extends through said roof, said barrier being located in a position near the end region of the case to form an arc-trapping compartment located substantially directly above said circuit element and causing an arc spark to be deflected and to be quenched upon the outer end portion of said contact element, said barrier acting as a shield between said arc discharge within said case and said actuator, an integrally formed projection on the top of one end of each case section and a recess in the top of the other end of each case section, said respective projections being nested in respective recesses to extend over the seam line between said case sections and in the region above the contact element where arc discharge takes place whereby said discharge is prevented from penetrating into and through said seam line. 